However, this research showed that pre-term babies who exclusively received breast milk for at least three-quarters of the days spent in hospital showed improved brain connectivity, compared to babies who consumed less.

"Our findings suggest that brain development in the weeks after pre-term birth is improved in babies who receive greater amounts of breast milk," said James Boardman, Director of the Jennifer Brown Research Laboratory at the University of Edinburgh.

"The study highlights the need for more research to understand the role of early life nutrition for improving long-term outcomes for pre-term babies, he added.

Premature birth is associated with the possibilities of an increased risk of the decline of cognitive skills in later life, which are thought to be linked to alterations in brain development.

Helping mothers to provide breast milk in the weeks after giving birth could improve long-term outcomes for children born pre-term, the researchers noted, in the paper published in the journal NeuroImage.

"Mothers of pre-term babies should be supported to provide breast milk while their baby is in neonatal care -- if they are able to and if their baby is well enough to receive milk -- because this may give their children the best chance of healthy brain development," Boardman said.

For the study, the team analysed MRI brain scans of a small number of babies.

The babies were born before 33 weeks gestation and scans took place when they reached term-equivalent age, an average of 40 weeks from conception.

The effects were greatest in babies who were fed breast milk for a greater proportion of their time spent in intensive care.